Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$83.30	3.417%	$86.1464	$86.15	$86.15	$86.10
Purchase #2	$143.58	11.519%	$160.119	$160.12	$160.10	$160.10
Purchase #3	$20.43	4.155%	$21.2789	$21.28	$21.30	$21.30
Purchase #4	$71.83	4.229%	$74.8677	$74.87	$74.85	$74.90
Purchase #5	$243.61	11.284%	$271.099	$271.10	$271.10	$271.10
Purchase #6	$78.88	3.820%	$81.8932	$81.89	$81.90	$81.90
Purchase #7	$162.34	4.460%	$169.5804	$169.58	$169.60	$169.60
7 purchase totals =	$803.97		$864.9846	$864.99	$865.00	$865.00